Conventionally, a key is inserted into key grooves formed on both the rotary body and the rotary shaft when a rotary body such as a pulley and a gear is to be fixed to a rotary shaft. This provides a direct power transmission between the rotary shaft and the rotary body even when an over-load force and an impact force occur at the rotary shaft, and has often produced troubles even with other elements.
On the contrary, the rotary body and the rotary shaft can be fixed by screws inserted in a traversal direction of the rotary shaft. However, this method makes less fixing strength, and occasionally more troublesome in the process of attaching screws, especially at the narrow area, because the screws have to be inserted in the traversal direction of the shaft.
Accordingly, it is an object of the invention to provide a device for fixing a rotary body to a rotary shaft which solves the above problems. The invention permits a slippage between the rotary body and the rotary shaft when an unexpected force such as an over-load force and an impact force occurs, but normally provides an appropriate fixing strength therebetween when both rotary body and shaft rotate together.